1. Field of the Invention
The present invention relates to an improvement in a motor-driven power steering unit support structure.
2. Description of Background Art
A motor-driven power steering unit support structure according to the background art is known, wherein a motor-driven power steering device is supported by brackets attached to a vehicle body frame (see, for example, Japanese Patent No. 2663454).
FIGS. 2 and 3 in Japanese Patent No. 2663454 show that a steering shaft 7 is supported by an upper-side frame pipe 101 and a lower-side frame pipe 102 which constitute a vehicle body frame 1. The steering shaft 7 is divided into an upper side 7a and a lower side 7b. A motor-driven power steering device 8 is interposed between the upper side 7a and the lower side 7b. The power steering device 8 is mounted onto the upper-side frame pipe 101 through brackets 9. With the above construction, the motor-driven power steering device 8 is supported in the axial direction of the steering shaft 7.
In the background art, if the steering shaft 7 is supported at two upper and lower positions of the vehicle body frame 1, a mounting error may be generated in mounting the steering shaft 7 due, for example, to production errors in the upper-side frame pipe 101 and the lower-side frame pipe 102 of the vehicle body frame 1. The error is, for example, an error in a direction orthogonal to the steering shaft 7.
Therefore, even in the case where the mounting error in mounting the brackets 9 onto the upper-side frame pipe 101 is small, the error present between the motor-driven power steering device 8 and the brackets 9 in a direction orthogonal to the steering shaft 7 is difficult to absorb at the time of supporting the motor-driven power steering device 8 by the brackets 9 in the axial direction of the steering shaft 7.
In addition, the motor-driven power steering device 8 is supported by the left and right brackets 9, 9. Therefore, the motor-driven power steering device 8 can be firmly supported against external forces exerted thereon in the vehicle width direction. However, the motor-driven power steering device 8 is liable to be displaced by an inertial force in the front-rear direction generated in the motor-driven power steering device 8, which is a heavy body, in the case where the vehicle is accelerated or decelerated, for example.